Which option best reflects a functional requirement of a system?

The correct answer effectively captures the essence of a functional requirement, which specifically addresses what the users need to accomplish with the system. Functional requirements outline the specific behaviors and functions that the system must exhibit to satisfy user needs. For instance, it may detail tasks like processing transactions, generating reports, or allowing user authentication—all of which are directly related to user interactions with the system. Clearly articulating what users should be able to do ensures that the final product aligns with user expectations and business goals.

In contrast, the other options represent different aspects of a system's overall design or implementation. Describing operational costs relates to the financial implications of running the system rather than its direct functionalities. Detailing security measures involves safeguards put in place but does not specify user interactions. Outlining hardware specifications refers to the physical components necessary to run the system, which does not encapsulate the functional capabilities necessary for user operation. Thus, focusing on user capabilities correctly identifies the core of functional requirements.